This invention relates generally to eddy current testing methods and apparatus, and more particularly to an eddy current type of method and apparatus for measuring deflection profiles, radius of curvature, and the like.
Angle, displacement and deflection measurements based on dimensional, electromechanical, gravitation and other principles are generally known and heretofore have used a variety of apparatus such as dowel pins, machine gauges, capacitance devices and linear variable differential transformers.
Eddy current type surface probes are also known. In such apparatus, eddy currents are produced in an electrically conductive test piece by a coil through which an alternating current flows, and as a result of the eddy currents produced therein, impedance of the coil and the voltage applied to the coil are changed and thus the measurement of a particular characteristic of the surface is determined by a measured change in impedance of the sensor coil. However, state of the art angle and displacement measuring devices are normally operator dependent and typically require direct line of sight or line of measurement accessibility of the specimen and thus cannot be used in the interior of elongated closed structures such as curved metal pipes or tubes.